Petr Virostko

Ion current to a substrate in the pulsed dc hollow cathode plasma jet deposition system

A current of positive ions to a substrate was studied in the pulsed dc hollow cathode plasma jet system for deposition of thin films working at low pressures. The time evolution of electric current to a planar probe with pulsed negative dc bias was measured. The pulsing of the bias of the probe was applied to allow measurements with a dielectric film being deposited on its surface. The frequency of pulsing of the probe bias was higher than the frequency of pulsing of the discharge. The time evolution of the ion current density to the probe ji was determined for the whole period of modulation of the discharge for a discharge repetition frequency of 2.5 kHz and different duty cycles D. The mean ion current density ji, averaged over the whole period of the discharge, increased with decreasing D although the value of the mean discharge current was kept constant. A simple analytical model is proposed to explain this effect. It is shown that the observed rise in ji with decreasing D is in major part caused by the rise in the ion current in the afterglow region of the pulsed discharge.

Holographic Interferometry of Barrier-Torch Discharge in Argon and Helium

Holographic interferometry of atmospheric RF barrier-torch discharge burning in argon and helium is reported. Holographic interferometer of Mach–Zehnder type with He–Ne laser was used for temperature measurement of neutral particles of working gas. Interference pattern was registered by a high-speed charge-coupled devices (CCD) camera. Resulting temperature ranged from 330 to 450 K. A slight difference between temperatures measured close to the glass nozzle outlet and close to the substrate was observed.

Space Resolved Optical Emission Spectroscopy During Deposition of BaxSr1-xTiO3 Thin Films by Double Hollow Cathode Plasma Jet System

Pulse modulated double hollow cathode RF plasma jet system with two separate independent nozzles made of BaTiO3 (BTO) and SrTiO3 (STO) was used for deposition of BSTO thin films on Si and on multi-layer Si/SiO2/TiO2/Pt substrates. Dielectric properties of BSTO layers strongly depend on ratio composition expressed by parameter x = Ba/(Ba+Sr) and on accuracy in presence of other elements. Space resolved optical emission spectroscopy (OES) was used mainly for monitoring of concentration of particles sputtered from the hollow cathode and for feedback correction of power supplied in both nozzles because applied power was responsible for sputtering speed of Ba and Sr particles. Main attention was focused on relation between ratio of spectral intensity of Ba, Ba+, Sr and Sr+ lines close to substrate and ratio of Ba and Sr concentration in the deposited film. 2D map of emission lines intensity distribution for Ba, Ba+, Sr, Sr+, Ti, Ar, and Ar+ for double hollow cathode plasma jet system with BTO and STO nozzles was created. OES was also used for observing of excess of Ti particles in final layer with negative effect on layer properties and for measurement of rotational temperature of OH radicals. Preliminary results of all these optical measurements are published in this paper. Deposited thin films were analyzed by X-ray diffraction, which confirmed presence of BSTO and STO perovskite phase in the films, by atomic force microscopy (AFM), by electron microprobe and by micro-Raman scattering measurement.

Measuring the Ion Flux to the Deposition Substrate in the Hollow Cathode Plasma Jet

Measurements of positive ion flux to a negatively biased substrate for deposition of TiOx thin films by the hollow cathode plasma jet system are presented. Different methods of obtaining the bias of substrate and measuring the resulting ion flux were used for different bias frequencies. Pulsed DC bias, middle frequency 500 kHz bias, and 13.56 MHz RF bias were compared. For 13.56 MHz two different methods of ion flux determination were used. These measurements were performed for different bias voltage and discharge conditions.